Earth Science Unit 9 Study Guide

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Questions and Answers

What factors affect the deformation of a rock?

temperature, pressure, rock type, time

What is the difference between brittle deformation and ductile deformation?

Brittle deformation occurs near the surface under less pressure and heat, leading to fractures, while ductile deformation happens deep beneath the surface, allowing rocks to change shape without fracturing.

Would rock in the lower mantle undergo brittle deformation or ductile deformation? Explain.

It will probably undergo ductile deformation.

What are the four types of stress that affect rocks? Describe them.

Tensional stress pulls rocks apart; compressional stress squeezes rocks; shear stress distorts rocks; confining stress squeezes rocks causing folding or fracturing. Signup and view all the answers

What is isostatic adjustment?

The earth's crust establishing a new level of gravitational balance. Signup and view all the answers

What are the different types of folds?

Anticlines, synclines, and monoclines. Signup and view all the answers

What is a syncline?

Downfolds or troughs. Signup and view all the answers

Describe the four main types of faults in terms of the motion along each type.

Normal fault: hanging wall moves down; reverse fault: hanging wall moves up; thrust fault: reverse fault with dip less than 45 degrees; strike-slip fault: movement is horizontal along the fault line. Signup and view all the answers

What are the major types of mountains?

Volcanic, folded, and fault-block mountains. Signup and view all the answers

How would you classify a mountain range made up of numerous thrust faults?

Folded mountains. Signup and view all the answers

What is a horst?

An elongated valley bordered by relatively uplifted structures. Signup and view all the answers

What is a graben? In what type of mountains are grabens most commonly found?

A ditch or trench, commonly found in fault-block mountains. Signup and view all the answers

Define plateau, dome, and basin in your own words.

Plateau: high elevated flat land; dome: upwarping creating a circular shape; basin: downwarping forming a circular shape. Signup and view all the answers

What mountains form along convergent plate boundaries?

Volcanic mountains (ocean-ocean convergence), volcanic and folded mountains (ocean-continental), folded mountains (continent-continent). Signup and view all the answers

What mountains form along divergent plate boundaries?

Fault-block mountains made of volcanic rock. Signup and view all the answers

Why can't continental crust be subducted?

It's less dense than the mantle. Signup and view all the answers

Compare mountain building along an ocean-continent convergent boundary and a continent-continent convergent boundary.

Ocean-continent boundaries can form volcanic arcs through subduction or create folded and faulted mountains. Continent-continent boundaries create folded mountains as continental crust does not subduct. Signup and view all the answers

How does accretion affect continents and mountain building?

When continents meet, the rock faults or folds and is thrust upward and downward, forming mountains. Accretion increases the size of tectonic plates. Signup and view all the answers

What is a terrane?

Any crustal fragment that has a geological history distinct from that of the adjoining terranes. Signup and view all the answers

Study Notes

Factors Affecting Rock Deformation

Temperature, pressure, rock type, and time significantly influence how rocks deform.

Brittle vs. Ductile Deformation

Brittle deformation occurs near the surface with low pressure and heat; rocks fracture under stress.
Ductile deformation occurs deep underground with high temperature and pressure; rocks change shape or size without fracturing.

Deformation in the Lower Mantle

Rocks in the lower mantle are likely to undergo ductile deformation due to extreme heat and pressure.

Types of Stress Affecting Rocks

Tensional stress: pulls rocks apart, causing extension.
Compressional stress: squeezes rocks, leading to shortening.
Shear stress: distorts rocks causing lateral movement.
Confining stress: applies uniform pressure, leading to folding or fracturing.

Isostatic Adjustment

Earth's crust adjusts to reach a new level of gravitational balance, often in response to the addition or removal of weight.

Types of Folds

Main types include anticlines (upward folds), synclines (downfolds or troughs), and monoclines (step-like folds).

Fault Motion Types

Normal fault: hanging wall moves down relative to footwall.
Reverse fault: hanging wall moves up relative to footwall.
Thrust fault: a type of reverse fault with a dip of less than 45 degrees.
Strike-slip fault: horizontal movement parallel to the fault trend.

Major Types of Mountains

Mountains are classified into volcanic, folded, and fault-block types based on their formation.

Mountain Classification

Mountain ranges with numerous thrust faults are classified as folded mountains.

Horst and Graben

A horst is an uplifted elongated landform bordered by valleys.
A graben is a down-dropped area or trench found mainly in fault-block mountains.

Geological Landforms

Plateau: elevated flat landform.
Dome: upwarped circular rock formation.
Basin: downwarped circular structure.

Mountains along Convergent Boundaries

Ocean-ocean convergence results in volcanic mountains.
Ocean-continental convergence results in both volcanic and folded mountains.
Continent-continent convergence predominantly forms folded mountains.

Mountains along Divergent Boundaries

Divergent boundaries create fault-block mountains composed mainly of volcanic rock.

Continental Crust Subduction

Continental crust cannot be subducted due to its lower density compared to the mantle.

Mountain Building Comparisons

Ocean-continental convergent boundaries create volcanic arcs and accretionary wedges, resulting in folded and faulted rock.
Continent-continent convergent boundaries produce folded mountains, as neither crust type is dense enough to subduct.

Accretion's Impact

Accretion causes faulting and folding where continental plates meet, contributing to mountain range formation and expanding plate size.

Terranes

A terrane is a crustal fragment with a geological history distinct from neighboring terranes.

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Description

This quiz covers key concepts from Earth Science Unit 9, focusing on rock deformation and the factors affecting it. Test your knowledge on brittle versus ductile deformation and the conditions under which these processes occur.